Relationship between Acoustic Firmness and Magness Taylor Firmness in Royal Gala and Golden Smoothee Apples

This study aimed to evaluate apple firmness measured using both the penetrometer and acoustic methods. The methodologies were applied to Royal Gaya and Golden Smoothee apples (Malus domestica. Borkh) harvested from 12 different orchards in Catalonia (Spain), on six different dates, and over three seasons. The relationship between firmness and physicochemical quality parameters was analyzed at harvest and post-harvest. The results obtained showed a noticeable correlation between Magness Taylor firmness and acoustic measurements in Royal Gala, but no correlation was found for Golden Smoothee. Fruit variety and storage had a clear influence on correlations between the two measurements. Measurements of Magnes Taylor and acoustic firmness seemed to correspond to different physical properties. Acoustic measurements seemed to be a good tool for evaluating changes in tissue firmness during long-term storage, especially for Golden Smoothee apples. The maturity of the fruit seemed to play a more important role in the measurement of Magnes Taylor firmness than in the measurement of acoustic firmness for the Royal Gaya variety.